How did Tomonaga develop QED during WWII?
During the war, I was isolated from Western physics, but I had access to earlier works by Dirac, Heisenberg, and Pauli. I began by considering the problem of divergences in quantum field theory. It is natural to think that a theory should give finite predictions, so I sought a method to subtract infinities systematically. I introduced a covariant cutoff and then renormalized the electron mass and charge, showing that all observable quantities become finite. I published this in Japanese in 1943, but it was not widely known until after the war. The essential point is that I relied on physical intuition: I imagined the electron as surrounded by a cloud of virtual particles, and I subtracted the effects that could not be measured. I am grateful to my colleagues in Japan who discussed these ideas with me, even under difficult conditions. This work later merged with Feynman's and Schwinger's approaches to form modern QED.
Ask Shinichiro Tomonaga the follow-up →